This study examined job characteristics and organizational supports as antecedents of negative work-to-nonwork spillover for 1178 U.S. employees. Based on hierarchical regression analyses of 2002 National Study of the Changing Workforce data and O*NET data, job demands (requirements to work at home beyond scheduled hours, job complexity, time and strain) had positive relationships, and job resources (autonomy and skill development) and organizational supports (flexible work arrangements and two work-life culture facets) had negative relationships to negative spillover, but not all relationships held when multiple predictors were examined. Organizational supports did not moderate relationships of job characteristics to negative spillover, and relative weights analysis indicated that job characteristics accounted for the majority of explained variance in negative spillover. The findings underscore the importance of job characteristics, and suggest that job characteristics and organizational supports both need to be considered when developing work-life policies intended to reduce employees' negative work-to-nonwork spillover. (Contains 2 tables.)